mtd/cfi: SST39VF3201B flash model not properly handled

Dear All,

as Wolfgang Denx suggested me, i am trying to use the u-boot CFI driver with a CFI flash (SSTVF3201B).

This flash chip allows erasing/writing blocks of 4 KBytes (called "sectors" in the SST datasheet), or 64 KBytes (called "blocks").

The command sequence table for this flash shows 2 different commands to operate on these 2 kind of blocks. 0x50 is for "sector erase" and "0x30" (the command used from u-boot CFI driver as AMD_CMD_ERASE_SECTOR) is for the 64KB "block" erase.

The issue:
now, u-boot CFI driver works fine on 64KB boundary ranges, but if i expect to erase a 4KB sector size i get a full 64KB block erased.

Proposed solution:
Initially, a single sector size definition would be good enough for this chip, so the user should specify if he wants a 64 or 4 KB sector to be used, using some CFG_X.
CFI driver, through queries, should be able to identify this particular chip so that it can be handled in a specific way from the CFI driver (cmd 0x50 for 4KB secotrs, or 0x30 for 64KB secotrs).

I am thinking about to post a patch on this.
Anyway, until new AMCORE board patch is not accepted, there is the chance this can result as a "dead code" if no-one use this flash chip except me.

So, before i start, please let me know how to proceed, maybe is better to use a specific flash.c for my board for now ?
Or if you think a patch can be useful, any suggestion on how to implement it is really welcome.

Best Regards,
Angelo Dureghello

Hi Angelo,

Yes. But please take a look at the CONFIG_FLASH_CFI_LEGACY config option. This enables the legacy CFI flash devices. And IIRC the SST flash chips are supported via this driver/extension.

Please see my comment above. And grep for CONFIG_FLASH_CFI_LEGACY to see how its used in the config header. And if necessary, you can always extend the CFI configuration in the JEDEC source:

drivers/mtd/jedec_flash.c

Thanks,
Stefan

Dear Stefan Roese,

thaks for the hint, anyway seems i am unfortunate whit this flash chip:

first of all, i would understand why a flash chip is defined/handled as leagacy. Can someone kindly clarify this ? SST39VF3201B is a 2M x 16, CFI compliant.

CFI legacy dont seems anyway to support 0x50 command for erasing a sector, i grepped and found "only" a CMD_CLEAR_STATUS as 0x50 that don't seems to fit the case. But the code is not trivial, and i can miss something of course.

Also, legacy flash_info_t don't have any field to define the erase sector command. But still, i am not sure this chip should be considered legacy.

I grepped for *3201* SST chip, only baord that seems to use it is

esd/common

and this board has her own flash.c

But still, has been suggested me to use CFI driver, so i need to know what the u-boot community would prefer as approach.

Still a note. I found issues in Linux also for this chip (STT39VF3201B) and had to ask for a patch on the command set to allow the correct erase command to be used.

So how should i proceed ?

Many thanks.

Best Regards
Angelo Dureghello